GAFF use

General Discussion
1

Using GAFF (general amber force field) to optimize butane, it’s giving a C-C-C angle of 131.1 degrees however UFF and MMFF give an angle of 111.1 degrees. Is this a problem with the force field of am I not understanding something?

Thanks.

2

Hi, I just try to reproduce what you told before about the butane molecule
(C-C-C) angle.

What I have here is:

111.3 - using GAFF
111.1 - using UFF
and
111.5 using MMFF94.

I’m using version 1.0.3

2012/9/15 John Doe helstreak@hotmail.com

Using GAFF (general amber force field) to optimize butane, it’s giving a
C-C-C angle of 131.1 degrees however UFF and MMFF give an angle of 111.1
degrees. Is this a problem with the force field of am I not understanding
something?

Thanks.

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3

I’ve used GAFF in the latest Avogadro version and 1.0.3, all on Windows 7 Ultimate 64-bit and I’m still getting incorrect results for bond angle and bond length.